The overall purpose of this research is the elucidation of all aspects of phosphoinositide metabolism, their involvement in the detailed organization and functioning of membranous structures and their participation in physiological phenomena. Their high rate of renewal is indicative of a fundamental role in cell membranes which these studies are designed to clarify. During the present project period one major goal is to study further the mechanism and significance of the stimulation by external agents of the turnover of phosphatidylinositol and other acid phospholipids in vitro, the phospholipid effect. The nature and characteristics of alpha-adrenergic receptors mediating this effect in rat pineal gland and other suitable tissues including neuroblastoma cell cultures and their close coupling to phospholipid metabolism are to be determined. The mechanism by which norepinephrine and other agonists exert their effects will be studied through the measurement of changes in the level of individual phospholipids and in the extent of incorporation of radioactive precursors. Alterations in incubation conditions, pulse chase experiments, assays of individual reactions of phospholipid metabolism and experiments with plasma membrane and other subcellular fractions will be used to elucidate the events occurring in stimulated tissues. Fatty acid patterns of phospholipid classes will be examined and changes in calcium fluxes resulting from the increased phospholipid turnover will be measured. The other major goal is the elucidation of the redirection of phospholipid metabolism by cationic amphiphilic drugs, such as propranolol and psychoactive agents. The spectrum of drugs capable of causing this effect in vitro, possibly through inhibition of phosphatidate phosphohydrolase, will be determined and compared with those drugs able to cause human phospholipidosis in chronic use. The mechanism of the phenomenon is to be explored, especially in relation to calcium ions and charges on cell membrane constituents. The role of inositol in influencing and controlling metabolic processes and lipid interconversions will also be analyzed.